Apparatus for controlling fluid flow rate

ABSTRACT

A variable infusion device for administering liquids parenterally to a patient is formed of inexpensive plastic members. The device includes an elongated passage defined between two members of the device which are bonded to one another. A third member is movable relative to the first and second members to change the length of the elongated passage through which liquid flows thereby changing the flow rate of the liquid through the device. The liquid flow rates to the patient can be incrementally adjusted over a wide range of flow rates. Settings also include a low flow rate for merely keeping the patient&#39;s vein open.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for controlling fluidflow rate. More particularly, the invention relates to a variableinfusion device for administering liquids parenterally to a patient.

The administration of liquids parenterally to a patient is a treatmentthat has been employed for many years. It typically involves the use ofa container of liquid to be infused, an elongated flexible tube forconveying the liquid from the container to a patient and a cannula orcatheter for insertion into the cardiovascular system of the patient tointroduce the liquid for infusion into the patient's system A variety ofliquids may be infused in this manner, including dextrose, saline,Ringers solution, and water or any combinations of these solutions.Others include whole blood and plasma. More recently, drugs such asantibiotics, heprine, etc. are administered in this manner.

In past, the most common manner of controlling the flow of the liquidbeing administered to the patient has been to selectively collapse aportion of the flexible delivery tube using a roller clamp, for example.The rate of flow in such cases is determined by the rate at which dropsof liquid are observed falling through a conventional drip chamber.While this arrangement for administering liquids parenterally has beensatisfactory where the desired flow rates are comparatively fast and theaccuracy of the flow rate is not crucial, it is not suitable where veryaccurate or very low flow rates are necessary as, for example, where adrug must be administered to a patient at a very low constant flow rateover an extended period of time or where a very low flow rate is desiredmerely to keep intervenous cannulas and catheters from becoming cloggedwith clotting blood until further administration of liquid medicationsis desired.

An object of the present invention is to provide a variable infusiondevice for administering liquid parenterally to a patient which avoidsthe aforementioned drawbacks of this known arrangement for controllingthe flow of parenteral fluids to a patient. More particularly, an objectof the invention is to provide a variable infusion device foradministering liquids parenterally which may be placed at any point in asupply line between a container of liquid to be administered to apatient and the patient for accurately controlling the liquid flow ratesover extended periods of time at a desired flow rate which may includevery low flow rates.

A further object of the invention is to provide a variable infusiondevice for administering liquid parenterally to a patient whichregulates the flow of liquid by selectively varying the effective lengthof the flow passage through the device.

An additional object of the invention is to provide a variable infusiondevice for administering liquid parenterally to a patient which can bemanufactured at relatively low cost with a minimum number of parts foreconomical use in a wide variety of applications.

These and other objects of the invention are attained by the variableinfusion device of the present invention which comprises means definingan elongated passage through which a liquid can be flowed, and means forchanging the flow rate of a liquid flowing through the elongatedpassage. The means for changing the flow rate includes means forchanging the length of the elongated passage through which the liquid isflowed thereby changing the flow rate of the liquid. The means definingan elongated passage includes a first member having an elongated groovewith a small cross-sectional area formed in a surface thereof and asecond member having a surface overlying the groove. The means forchanging the length of the elongated passage through which the liquid isflowed comprises a third member having means for selectively bypassingthe liquid about at least a portion of the elongated passage definedbetween the first and second members through a bypass passage. The firstand second members are secured against movement relative to one anotherin the device. As a result, an effective liquid seal about the elongatedpassage between the first and second members can be maintained even inthe case both members are formed of a plastic material, for example.According to the preferred embodiment, the first and second members arebonded to one another. The third member is formed of an elastomericmaterial which is pressed against a surface of one of the first andsecond members to form a liquid seal therewith, while permittingrelative movement between the third member and the assembly of the firstand second members for selectively bypassing the liquid about at least aportion of the elongated passage defined between the first and secondmembers.

At least one of the first and second members has a plurality of spacedopenings communicating with respective portions of the elongated passagedefined between the first and second members. The third member ismovable relative to the spaced openings to selectively communicate abypass passage with respective ones of the openings to thereby changethe length of the elongated passage through which liquid is flowed. Thethird member closes the other openings while communicating a selectedone of the openings with the bypass passage. In the disclosedembodiment, the first, second and third members are retained within adial cover of the device.

The disclosed variable infusion device also includes a fourth memberhaving an additional elongated groove formed in a surface thereof. Anadditional surface of the second member overlies the additional groove.The second member is secured against movement relative to both the firstand fourth members. In the preferred form of the invention, the secondmember is bonded to both the first and fourth members to form anassembly. The assembly is mounted upon a connector housing of the devicevia the fourth member. The connector housing is provided with an inletand an outlet at the respective ends of the means defining an elongatedpassage for communicating liquid to and from the device. The secondmember of the device is preferably formed of a plastic material which ischemically bonded to the first and fourth members.

These and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in connection with the accompanying drawings which show, forpurposes of illustration only, one embodiment in accordance with theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a variable infusion device according to apreferred embodiment of the invention;

FIG. 2 is a side view from the right side of the variable infusiondevice shown in FIG. 1;

FIG. 3 is a rear or back view of the device illustrated in FIG. 1;

FIG. 4 is a front view of the outer side of the connector housing of thedevice of FIG. 1 which corresponds to the side of the device as shown inFIG. 3;

FIG. 5 is a top view of the connector housing shown in FIG. 4;

FIG. 6 is a sectional view of the connector housing taken along the lineVI--VI in FIG. 4;

FIG. 7 is a rear or back view of the inner side of the connector housingas shown in FIG. 4;

FIG. 8 is a sectional view of a portion of the connector housing takenalong the line VIII--VIII in FIG. 7;

FIG. 9 is an enlarged top view of an indicating an alignment tab of theconnector housing taken from the right side of FIG. 8;

FIG. 10 is a sectional view of the connector housing taken along theline X--X in FIG. 7 and showing the inlet and outlet of the device ofFIG. 1 in cross-section;

FIG. 11 is a sectional view of the connector housing taken along theline XI--XI in FIG. 5;

FIG. 12 is a sectional view of a portion of the connector housing takenalong the line XII--XII in FIG. 4;

FIG. 13 is a sectional view through the center of the assembled deviceof FIG. 1 with the dial in the ON position;

FIG. 14 is an edge side view of one metering plate of the device of FIG.1 and illustrating two projections provided on the plate having passagesextending therethrough for communicating with the inlet and outlet ofthe connector housing;

FIG. 15 is a right side view of the metering plate shown in FIG. 14illustrating an elongated groove formed in the surface of the plate andextending from the passage in communication with the inlet in an arrayof concentric convolutions to an inner end spaced from the passage inthe plate communicating with the outlet in the connector housing andalong the same radius of curvature as the passage in the platecommunicating with the inlet;

FIG. 16 is front view of a baffle plate of the device shown in FIG. 1;

FIG. 17 is a side edge view of the baffle plate of FIG. 16;

FIG. 18 is a side edge view of another metering plate of the variableinfusion device shown in FIG. 1;

FIG. 19 is a right side view of the metering plate of FIG. 1illustrating in dashed lines a serpentine shaped groove formed in theback or left side of the plate as shown in FIG. 18 with a series ofpassages extending through the plate at intervals along a circle aboutthe center of the plate where a passage is provided for communicationwith the outlet of the connector housing by way of correspondingpassages in the baffle plate of FIGS. 16 and 17 and the metering plateof FIGS. 14 and 15;

FIG. 20 is an inner side view of a shunt of the variable infusion deviceshown in FIG. 1;

FIG. 21 is a sectional view of a portion of the shunt taken along theline XXI--XXI in FIG. 20 illustrating a groove in the shunt which formsa bypass passage with the surface of the adjacent metering plate in theassembled device;

FIG. 22 is a side elevational view, partially in a cross-section, of theshunt taken from the right side of FIG. 20;

FIG. 23 is of the back or outer side of the shunt as shown in FIG. 20;

FIG. 24 is a sectional view of a portion of the shunt taken along theline XXIV--XXIV in FIG. 23

FIG. 25 is an inner side view of the dial cover of the variable infusiondevice of FIG. 1;

FIG. 26 is an edge side view of the dial cover taken from the right sideof FIG. 25;

FIG. 27 is a view of the back or outer side of the dial cover as shownin FIG. 25;

FIG. 28 is an enlarged cross-sectional view of the dial cover takenalong the line XXVIII--XXVIII in FIG. 27; and

FIG. 29 is a schematic drawing illustrating the variable infusion deviceof FIG. 1 and used in the flow line for controlling the flow of an IVsolution from an IV solution bag to a patient.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT

Referring now to the drawings, the variable infusion device 1 accordingto the preferred embodiment of the invention is formed of a connectorhousing 2, a KVO (keep vein open) metering plate or disc 3, a baffleplate 4, a metering plate 5, a shunt 6 and a dial cover 7. Thesecomponents are assembled as shown in FIGS. 1-3, 13 and 29 to form thevariable infusion device 1.

The device is useful for administering liquids parenterally to apatient. The Poiseuille equation defines the relationship between thelength and diameter of a tube and the fully developed laminar flow rateof a fluid through the tube. The variable infusion device 1 of theinvention operates in accordance with this relationship in that thelength of the elongated liquid passage through the device can beincrementally varied, so that a series of predetermined liquid flowrates can be achieved. When the device is used in the manner illustratedin FIG. 29, liquid from an IV solution plastic bag 8 passes through aclear drip chamber 9 to the inlet 10 of the device 1, then flows throughan elongated passage in the device 1 and exits from the device throughan outlet 11. It is then conveyed to a patient 13 through a clearplastic tube 12 by way of a connector 14 and a needle set 15. See FIGS.2, 3 and 29. The length of the elongated passage through the device 1can not only be incrementally varied to adjust the flow rate of theliquid through the device and to the patient, but also the passage canbe completely closed or blocked in the device 1 to stop the flow orcompletely opened to provide unrestricted flow.

Adjustments in the flow rate are made by rotating the assembly of dialcover 7 and shunt 6 of the device relative to a connector housing and asub-assembly of metering plates and a baffle plate which isnon-rotatably secured to the connector housing. Any one of twelvedifferent settings, shown on the dial cover 7 in FIG. 1, can be selectedby the operator by moving the desired indicium on the dial cover to aposition relative to an indicating and alignment tab 16 formed on theconnector housing 2. Namely, the possible positions include: an OFFposition where no flow is permitted through the device 1; an ON positionwhich provides a short, relatively large cross-sectional area passagefor relatively unrestricted flow of liquid through the device; and aseries of nine numerically labelled positions which can be individuallyselected to incrementally vary the flow rate through the device 1 from,for example, 83 milliliters per hour to 250 milliliters per hour, asillustrated on the dial cover 7 in FIG. 1. The plurality of respectiveflow rates are attained because the rotation of the dial cover 7 toposition the respective indicia thereon relative to the tab 16 resultsin incremental changes in the effective length of the elongated passagefor the liquid flowing through the device. Alignment of the KVO dialposition with the tab 16 causes the liquid to flow through a lengthypassage within the device 1 to restrict the flow rate to only a fewmilliliters per hour. This amount corresponds to that necessary to keepthe patient's vein open while administering only a minimum of liquidparenterally to the patient. The liquid administered with the device 1can be any liquid suitable for parenteral administration, includingdextrose, saline, Ringers solution, and water or any combination ofthese solutions. Drugs such as antibiotics, heparin, etc., can also beadministered as will be readily apparent to the skilled artisan.

The connector housing 2 is formed with the inlet 10 and outlet 11located on the outer side thereof. Passages 17 and 18 extend from theinlet 10 and outlet 11, respectively, through the connector housing torespective female fittings 19 and 20. The outlet passage 18 is coaxialwith the center of the circular connector housing 2 at the fitting 20.

The indicating and alignment tab 16 is integrally formed with theconnector housing 2. Grooves 21 and 22 are formed in the housing onopposite sides of the tab 16 as shown in FIG. 9. The outer free end ofthe tab 16 projects axially outward from the inner side of the connectorhousing for cooperation with the dial cover 7. A channel 23 is formed inthe outer side of the connector housing 2. The channel can be used toguide the clear plastic IV tube 12 connected to the outlet 11 of thedevice. A similar tube is connected to the inlet 10 through anappropriate fitting for conveying liquid to the device 1. Alternatively,as shown in FIG. 29, a clear drip chamber can be connected directly tothe inlet 10. The connector housing 2 is preferably integrally formed ofa plastic material as by molding. One suitable material is rigidpolyvinylchloride or polycarbonate. The outside surfaces of theconnector housing are preferably polished so as to be smooth to thetouch when adjusting the flow rate with the device 1. The diameter ofthe passages 17 and 18 in the connector housing 2 can be 1/8 inch and5/32 inch, respectfully, for example, so as not to offer any substantialresistance to the flow of liquid therethrough.

The KVO metering plate 3 is in the form of a circular disc or platehaving projections 24 and 25 formed integrally therewith on one side ofthe plate 3. The projections are adapted to mate with the respectivefemale fittings 19 and 20 of the connector housing 2 in the assembledcondition as shown in FIG. 13. The projections 24 and 25 are formed withpassages 26 and 27 therethrough for alignment with the passages 17 and18 in the connector housing 2 at one end thereof. The passages extendthrough the metering plate 3 from the projections 24 and 25 to theopposite side of the metering plate. The passage 27 for the outgoingliquid flow is coaxial with the center of the metering plate 3.

The side of the metering plate 3 opposite the projections 24 and 25 isformed with an elongated groove 28 which extends from the passage 26 inan array of concentric convolutions to an inner end 29 spaced from thepassage 26 along the same radius of curvature as the passage 26 withrespect to the central axis of the plate 3 extending through the centerof the passage 27. Particularly, the inner end 29 is spaced an angle of60° from the passage 26 as shown in FIG. 15. The groove 28 has asubstantially smaller cross-sectional area than the passage 26communicating therewith. For example, the groove 29 can have asemi-circular shape as seen in cross-section with the radius thereofbeing less than 0.015 inch. The small size of the groove 29 and also theconsiderable length thereof serve to reduce the flow of the liquidtherein to only a few milliliters per hour. This amount is sufficient tokeep a patient's vein open while minimizing the volume of liquidadministered. In the illustrated embodiment the pitch between theadjacent circular segments of the groove 29 is 0.048 inch. The passage26 and the inner end 29 of the groove 28 are located on a circle aboutthe passage 27 having a diameter of 0.500 inch in the illustratedembodiment. The surface of metering plate 3 with the elongated groove 28formed therein is flat within 00.002 T.I.R. and has a non-reflectivefinish. The opposite surface of the plate is polished. The plate ispreferably formed of a molded plastic material such as polysulfoneplastic.

The baffle plate 4 of the device 1 as shown in FIGS. 16 and 17 is athin, flat circular member with the same outer diameter as the meteringplate 3, for example, 1.502 inches. The plate 4 is formed with fourthrough passages 30-33 as shown in FIG. 16. Each of the passages has adiameter of 0.060 inch, which corresponds to the diameter of thepassages 26 and 27 in the metering plate 3. The passage 30 extends alongthe center axis of the circular plate 4 for axial alignment with thepassage 27 of the plate 3 in the assembled condition as shown in FIG.13. The three passages 31, 32 and 33 are spaced 60° from one anotherabout a circle having its center through the central axis of the plate 4and having a diameter of 0.500 inch. The middle passage 32 of the threepassages is adapted to be aligned with the passage 26 in the KVOmetering plate 3 in the assembled condition shown in FIG. 13. One of theother passages 31 and 33 is coincident with the inner end 29 of theelongated groove 28 in the metering plate 3 in the device 1. The twopassages 31 and 33 are symmetrically positioned with respect to a centerline of the baffle plate 4 passing through the passages 30 and 32 asshown in FIG. 16, so that the device 1 will be operable even if theplate 4 is turned 180° about this center line during assembly.

The baffle plate 4 has a thickness of 0.015 inch in the illustratedembodiment. The plate 4 is formed of a plastic material which can bechemically bonded at its respective surfaces to the adjacent meteringplates 3 and 5. Preferably, the baffle plate 4 is formed of apolysulphone plastic material such as a Union Carbide Udel P1700 grade.The assembly of the metering plate 3, baffle plate 4 and metering plate5 are chemically bonded to one another by immersing plate 4 incyclohexanone solvent and then welding or bonding the three memberstogether under the application of pressure. In the assembled condition,the metering plates 3 and 5 and intermediate baffle plate 4 are securedagainst movement relative to one another as a result of their bondedsurfaces. Further, the baffle plate 4 which is bonded to the meteringplates 3 and 5 forms a liquid tight seal against the surfaces of themetering plates to close the elongated grooves formed in the surfaces ofthe plates and thereby form elongated passages with the grooves of themetering plates for the flow of liquid through the device.

The metering plate 5 is shown in detail in FIGS. 18 and 19. The plate 5is a thin, flat circular member which, in the illustrated embodiment hasa thickness of 0.040 inch and a diameter of 1.504 inch. It is preferablyformed of molded polysulphone, the same plastic used for the meteringplate 3 and baffle plate 4. A serpentine-shaped groove 34 is formed inone surface of the metering plate 5 as shown in FIGS. 18 and 19. Thegroove may have a width of 0.025 inch and a depth of 0.015 inch, forexample, and extends in serpentine fashion completely around thecircular plate 5. A central through hole 35 is formed in the meteringplate 5. The hole 35 has a diameter of 0.060 inch and is adapted to bealigned with the corresponding holes in the baffle plate 4, KVO meteringplate 3 and connector housing 2 as illustrated in FIG. 13.

Twelve, equally spaced through holes or passages 36-47 are also formedin the metering plate 5 along a circle about the center of the circularplate. The hole 36 has a diameter of 0.060 inch. It communicates withone end of the serpentine-shaped groove 34 and is adapted to be alignedwith the passage 32 in the baffle plate 4 and cooperating passages inthe KVO metering plate 3 and connector housing 2 as illustrated in FIG.13 of the drawings. The other eleven holes 37-47 are spaced every 30°about a circle having a diameter of 0.500 inch. The holes 37-47 have adiameter of 0.040 inch. There is no hole in the adjacent baffle plate 4adapted to be aligned with the hole 37 in the metering plate 5 in orderto provide an OFF position to interrupt flow through the device asdiscussed hereinafter. The hole or passage 38 in the assembled conditionof the device is coincident with one of the passages 31 and 33 in thebaffle plate 4 which in turn communicates with the end of the elongatedgroove 28 in the KVO metering plate 3. Passages 39-47 are eachcommunicated with respective portions of the serpentine-shaped groove 34for incrementally changing the length of the groove 34 through whichliquid is flowed and thereby changing the flow rate through the device 1as discussed more fully hereinafter. Both sides of the metering plate 5are flat within 0.002 T.I.R. The surface of the metering plate 5 havingthe groove 34 formed therein is molded against a flat polished surfaceso that it has no flash projecting beyond the surface. The baffle plate4 overlies the surface of the metering plate 5 having the groove 34formed therein to form an elongated passage with the groove andsurrounding plate 5. The baffle plate 4 is chemically bonded to themetering plate 5 as well as the KVO metering plate 3 in a fluid typemanner, so as to effectively seal the elongated passages againstleakage. The surface of the metering plate 5 opposite that having thegroove 34 formed therein is flat and polished, so that the parting lineformed thereon during the molding of the plate is flat with thesurrounding surface to within 0.002 T.I.R. This surface of the plate 5is adapted to be engaged in sealing, sliding relationship with the shunt6 in the assembled condition of the device depicted in FIG. 13.

The shunt 6 shown in FIGS. 20-24 is a circular-shaped member having adiameter of 0.684 inch. The shunt is formed of an elastomeric materialsuch as a synthetic rubber, by molding. The surface 49 thereof shown inFIGS. 20-22 is molded against a flat polished surface, so that it issufficiently flat to form a seal against the adjacent surface of themetering plate 5 in the assembled condition of the device 1. The surface49 of the shunt 6 is formed with a groove 50 therein. The depth of thegroove is 0.050 inch. The bottom of the groove is rounded as shown inFIG. 21. The groove 50 and the cooperating surface of the metering plate5 in the assembled condition form a passage for liquid flow from aselected one of the openings 37 and 39-48 in the adjacent metering plate5, to the through hole 36 in the plate 5 in the direction of the outlet11 of the device 1. The side of the shunt 6 opposite the surface 49 isformed with three grooves 51, 52 and 53 for receiving cooperatingprojections 54, 55 and 56 on the dial cover 7 in the assembled conditionto prevent relative rotation between the dial cover and shunt. A centralbutton 57 on the shunt 6 is adapted to project through a correspondingopening 58 in the dial cover 7. The button 57 of the shunt 6 serves as adistal septum (injection site). A protector cap (not shown) is providedover the button. When the patient needs an intravenous injection of adrug the hypodermic needle may be inserted through button 57 and thedrug injected directly into the outlet channel of the device 1 forflowing directly to the patient. This avoids the need to make lots ofpunctures in the patient's limited number of intravenous injectionsites.

Dial cover 7 is shown in detail in FIGS. 25-28. The dial cover isintegrally formed of a plastic material as by molding. The same plasticmaterial used to form the connector housing 2 can be used to form thedial cover. The dial cover 7 is circular in shape and is formed on oneside with an annular projecting portion 59 having a central opening 58therein for receiving the button 57 of the shunt 6. The opposite side ofthe dial cover is formed with a depending flange 60 formed of twelveaxially projecting flange portions 61-73 which are spaced from oneanother by axially extending slots 74. The slots permit the flangeportions 61-73 to be deflected slightly during adjustment of the device1 by interaction with the indicating and alignment tab 16 of theconnector housing. The outer, free end portions of the flange portions61-73 each include a radially inwardly protruding portion 75 having asurface 76 inclined at an angle of 30° with respect to the central axisof the dial cover. The indicating and alignment tab 16 of the connectorhousing cooperates with the respective inclined surfaces 76 foraccurately positioning the dial cover and shunt 6 associated therewithwith respect to the assembly of the metering plate 5, baffle plate 4 andKVO metering plate 3 which is non-rotatably positioned in the connectorhousing 2. The projections 54, 55 and 56 on the dial cover are receivedwithin grooves 51, 52 and 53 in the shunt as noted above, so that theshunt rotates with the dial cover during adjustment of the device 1.

The bonded assembly of the KVO metering plate 3, baffle plate 4 andmetering plate 5 is dimensioned to fit within the annular space definedby the depending flange 60 of the dial cover 7. To assemble the dialcover and the bonded assembly of the metering plates, the meteringplates are snap-fitted into position against the bias of the individualdepending flange portions 61-73 in cooperation with the inclinedsurfaces 76 thereon. The radially inwardly protruding portions 75 of theflanges 61-73 retain the assembly of the metering plates and baffleplate in position within the dial cover 7. The depth of the projectingportion 59 of the dial cover which receives the shunt 6 is slightly lessthan the height of the shunt 6, so that in the assembled condition ofthe device the shunt is compressed against the surface of the meteringplate 5 to form a liquid seal therewith while permitting relativerotation of the shunt with respect to the surface of the metering plate5 during adjustment of the variable infusion device 1. The projections24 and 25 on the KVO metering plate 3 are received within the femalefittings 19 and 20 of the connected housing and connected thereto as bysolvent bonding to prevent relative rotation of the connector housingand the assembly of the metering plates and baffle plate.

During use of the variable infusion device 1, the valve cover 7 can berotated with respect to the assembly of the metering plates and baffleplate and the associated connector housing to one of twelve differentpositions as indicated on the dial cover. In the OFF position, thegroove 50 of the shunt 6 is aligned with passage 37 in the meteringplate 5 and thus, passages within the device by the baffle plate 4, sothat liquid flow through the device is interrupted. In the ON position ashort, relatively large cross-sectional passage for liquid flow throughthe device 1 is provided by way of the inlet 10, passage 17 in theconnector housing 2, passage 26 in metering plate 3, passage 32 in thebaffle plate 4, passage 36 in the metering plate 5, groove 50 in theshunt 6, central passage 35 in metering plate 5, passage 30 in thecenter of baffle plate 4, passage 27 in the KVO metering plate 3 andpassage 18 in the connector housing 2 to the outlet 18. This provides arelatively unrestricted flow path for a liquid, so as not to appreciablychange the outgoing flow rate of the device 1 as compared with theincoming flow rate to the device.

When the variable infusion device 1 is adjusted to the setting KVO, theliquid flow is directed through the complete length of the elongatedpassage formed between the KVO metering plate 3 and baffle plate 4 inthe elongated groove 28 and then through one of the passage 31 and 33 ofthe baffle plate 4, passage 38 in the metering plate 5, groove 50 of theshunt 6 and on to the outlet 18 in the same manner as described withrespect to the ON position. Since the cross-sectional area of theelongated passage defined between the KVO metering plate 3 and baffleplate 4 is relatively small in comparison with the passages in thedevice leading to and from the elongated passage, and the length of thiselongated passage is relatively long, the flow rate through the device 1is relatively small, only a few milliliters per hour or that necessaryto keep the patient's vein open while minimizing the quantity of liquidinfused.

The other nine settings of the dial cover 7 result in liquid flowthrough the elongated passage defined between the baffle plate 4 and themetering plate 5 in the serpentine-shaped groove 34. In particular, eachsetting corresponds to a different length of the elongated passagedefined by the serpentine-shaped groove 34 and the baffle plate 4thereby to incrementally change the flow rate depending upon theselected setting by changing the length of the elongated passage throughwhich the liquid is flowed in the device 1. Thus, for example, asindicated on the dial cover in FIG. 1, the flow rate can be variedincrementally from 83 milliliters per hour to 250 milliliters per hours.Thus, the variable infusion device 1 of the invention permits theaccurate control of the flow rate of the IV solution from the plasticbag 8 shown in FIG. 29 to the patient 13. The use of a relatively smallnumber of components in the device 1, all of which may be formed ofplastic, also results in a relatively low cost and easily manufacturedvariable infusion device.

While I have shown and described only one embodiment in accordance withthe invention, it is understood that the same is not limited thereto,but is susceptible to numerous changes and modifications as known tothose skilled in the art. For example, the variable infusion device ofthe invention could be formed without the KVO elongated passage betweenthe metering plate 3 and baffle plate 4. An incremental adjustment ofthe flow rate through such a device would be based solely on changingthe length of the elongated passage defined by the groove in themetering plate 5 and the adjacent baffle plate 4 through movement of theshunt 6 relative to the assembly of the metering plate and baffle plate.Therefore, I do not wish to be limited to the details shown anddescribed herein, but intend to cover all such changes and modificationsas are encompassed by the scope of the appended claims.

I claim:
 1. A device for controlling a flow rate of a liquid to beadministered parenterally to a patient comprising means defining apassage through which a liquid can be flowed, and means forincrementally changing a flow rate of a liquid flowing through saidpassage, said means for incrementally changing the flow rate includingmeans for incrementally changing a length of said passage through whichsaid liquid is flowed thereby changing the flow rate of said liquidthrough said passage, wherien said means defining a passage includes afirst member having a flat surface with a groove formed therein radiallyoutward of an axis of rotation of said device and a second member havinga surface overlying said groove to from at least a portion of saidpassage with said groove and said first member, said first and secondmembers being secured against movement relative to one another in saiddevice, wherein said means for incrementally changing the length of saidpassage through which said liquid is flowed comprises a third memberhaving means for selectively bypassing said liquid about at least aportion of the passage defined between said first and second membersthrough a bypass passage of said third member and wherein at least oneof said first and second members has a plurality of spaced openingsextending therethrough in a direction transverse to said flat surface ofsaid first member and communicating with respective portions along thelength of said passage defined between the first and second members,said plurality of spaced openings being located radially outward of saidaxis of rotation of said device, said third member being rotatable withrespect to said first and second members about the axis of rotation ofsaid device so as to be movable relative to said spaced openings toselectively communicate said bypass passage with respective ones of saidopenings to thereby incrementally change the length of said passagethrough which said liquid is flowed.
 2. A device according to claim 1,wherein said first and second members are bonded to one another.
 3. Adevice according to claim 1, wherein that portion of the passage formedby the groove in said first member and the overlying surface of saidsecond member has a cross-sectional area on the order of 5×10⁻⁴ inch² orless.
 4. A device according to claim 1, wherein the passage definedbetween said first and second members extends in a serpentine shape. 5.A device according to claim 1, wherein an inlet opening is provided inone of said first and second members for communicating said liquid tothe passage defined between said first and second members, saidplurality of spaced openings serving as respective outlet openings whencommunicated with said bypass passage by said third member.
 6. A deviceaccording to claim 5, wherein said third member closes the other of saidoutlets while communicating a selected one of said outlets with saidbypass passage.
 7. A device according to claim 1, wherein said first,second and third members are retained within a dial cover of saiddevice.
 8. A device according to claim 1, wherein said means defining apassage further comprises a fourth member having an additional elongatedgroove formed in a surface thereof, an additional surface of said secondmember overlying said additional groove to form an additional portion ofsaid passage with said additional groove and said fourth member.
 9. Adevice according to claim 8, wherein said fourth member is mounted upona connector housing of said device, said connector housing having aninlet and an outlet at the respective ends of said means defining apassage for communicating liquid to and from said device.
 10. A deviceaccording to claim 8, wherein said second member is secured againstmovement relative to both said first and fourth members.
 11. A deviceaccording to claim 10, wherein said second member is bonded to both saidfirst and fourth members.
 12. A device according to claim 8, wherein anoutlet opening extends from said additional elongated groove throughsaid first and second members, said third member being rotatable aboutsaid axis of rotation relative to said outlet opening to selectivelycommunicate said bypass passage with the passage defined between saidsecond and fourth members.
 13. A device according to claim 1, wherein atleast said second member of said device is formed of a plastic materialwhich is chemically bonded to said first member.
 14. A device accordingto claim 1 wherein said third member is provided with means permittinginjection of a hypodermic needle into said device for introducing a druginto the liquid therein for administration to a patient.
 15. A devicefor controlling a flow rate of a liquid to be infused parenterally to apatient comprising a metering member having a flat surface with a grooveformed therein radially outward of an axis of rotation of said device, abaffle member having a surface overlying the groove of the meteringmember to form a passage with said groove and said metering memberthrough which a liquid can be flowed, said baffle member being securedagainst movement relative to said metering member, at least one of themetering member and the baffle member having a plurality of spacedopenings extending therethrough in a direction transverse to said flatsurface of said metering member and communicating with respectiveportions along the length of said passage, said plurality of spacedopenings being located radially outward of said axis of rotation of saiddevice, add a shunt rotatable about said axis of rotation relative tosaid metering member and baffle member for selectively communicatingwith respective ones of said plurality of spaced openings for bypassingliquid about at least a portion of the passage.
 16. A combination forvariable infusion of liquid parenterally to a patient comprising acontainer a container containing a liquid to be administeredparenterlaly to a patient, a needle set through which liquid form saidcontainer can be administered to a patient when a needle of said needleset is inserted into the patient, and means defining a flow path forconveying liquid from said container to said needle set, said meansdefining a flow path including a device for controlling a flow rate of aliquid from said container to be infused paraenterally to a patient viasaid needle set, said device comprising a metering member having a flatsurface with a groove formed therein radially outward of an axis ofrotation of said device, a baffle member having a surface overlying thegroove of the metering member to form a passage with said groove andsaid metering member through which a liquid can be flowed, said bafflemember being secured against movement relative to said metering member,at least one of the metering member and the baffle member having aplurality of spaced openings extending therethrough in a directiontransverse to said flat surface of said metering member andcommunicating with respective portions along the length of said passage,said plurality of spaced openings being located radially outward of saidaxis of rotation of said device, and a shunt rotatable about said axisof rotation relative to said metering member and baffle member forselectively communicating with respective ones of said plurality ofspaced openings for bypassing liquid about at least a portion of thepassage.